Basic biochemical research approaches have provided information on vocal fold vibration that is potentially useful for clinical decision making. However, a major challenge to voice scientists in the next decade will be to improve the scientific base for the clinical decisions made for patients with specific abnormalities of vocal production. This application for the First Award (R29) requests support to continue development of research in the combined fields of laryngeal physiology, pathophysiology, and biomechanics. The long range goals of this experimental work are to better understand both normal and pathological phonation and to contribute to the development of valid, comprehensive, and noninvasive clinically feasible methods of representing and measuring the physiology of phonation. This proposal has two related parts. The first addresses the physiology of specific vocal fold pathologies and how particular biomechanical variations are caused by pathology changes. An excised larynx model will be used to simulate abnormal vocal fold mechanical properties such as stiffness, tension, variations in approximation, and alterations in the vertical tension of vocal fold cover. The studies will measure the effects of stiffness, variations in the adduction of upper and lower lips of the folds, and asymmetry of the glottis and of vocal fold tension. The results of vocal fold mass changes, the specific effects of surgical augmentation of the vocal folds, and changes associated with dehydration of the vocal folds will also be examined. Measurements will be made of vocal fold stiffness, amplitude of vocal fold vibration, and mucosa epithelial wave. Additional measures will assess the stability and efficiency of vibrations, the phonation threshold pressure, vocal fold contact area, and the spatial distribution of the contact area and intraglottal stress. As a supplement to the excised larynx model, a finite element analysis (FEA) computer model and a mucosal wave model will be studied. The purpose of these series of systematic measurements of the effects of specific biomechanical variables is better to understand the mechanisms that result in abnormal phonation. The second part of this proposal focuses on development of a multiple-measurement approach in order to non-invasively evaluate the characteristics of vocal fold vibration patterns. This part of the study will integrate data from several different non-invasive approaches to improve the measurement of vocal fold vibration. Measurements using non-invasive methodologies will be compared to direct measurements in the excised larynx model of pathological conditions in order to establish validity and calibration for the non-invasive measures. The data from these controlled experimental studies will then be compared to data from a large database of simultaneously recorded multiple measurements from patients with known laryngeal pathologies.